As search for life in the universe
continues, scientists already know it's not enough to find rocky planets in a star's habitable zone, the region where a planet can host liquid water
Liquid water is just the
starting point Indeed, other factors, such as nitrogen, may play a role in a planet's habitability, as well as the ratio of land to sea.
A team of scientists suggests
that one of the key characteristics of a life-supporting, rocky exoplanet is that it must be young — just a few billion years old at most.
To support life, a planet needs
enough heat to power a carbon cycle, which is typically created due to the radioactive decay of elements such as uranium and thorium.
Lead author Cayman Unterborn, a
research scientist at the Southwest Research Institute said "Exoplanets without active degassing are more likely to be cold, snowball planets,"
That radioactive decay, in turn,
causes volcanic degassing — the release of gasses held within a planet into the atmosphere through volcanoes — on the surface of a planet.
Degassing contributes CO2 to
the atmosphere and continues the carbon cycle. But older planets might have consumed their radioactive resources and thus may not be able to retain their heat